drm/i915/execlists: Simplify gen12_csb_parse

Having decided that we only care about the promotion predicate, we can
simplify gen12_csb_parse to simply check whether we need to jump to a
new queue.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190925130845.17952-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -1801,9 +1801,6 @@ gen12_csb_parse(const struct intel_engine_execlists *execlists, const u32 *csb)
 	bool ctx_away_valid = GEN12_CSB_CTX_VALID(upper_dw);
 	bool new_queue = lower_dw & GEN12_CTX_STATUS_SWITCHED_TO_NEW_QUEUE;
 
-	if (!ctx_away_valid && ctx_to_valid)
-		return true;
-
 	/*
 	 * The context switch detail is not guaranteed to be 5 when a preemption
 	 * occurs, so we can't just check for that. The check below works for
@@ -1811,8 +1808,10 @@ gen12_csb_parse(const struct intel_engine_execlists *execlists, const u32 *csb)
 	 * instructions and lite-restore. Preempt-to-idle via the CTRL register
 	 * would require some extra handling, but we don't support that.
 	 */
-	if (new_queue && ctx_away_valid)
+	if (!ctx_away_valid || new_queue) {
+		GEM_BUG_ON(!ctx_to_valid);
 		return true;
+	}
 
 	/*
 	 * switch detail = 5 is covered by the case above and we do not expect a
@@ -1820,7 +1819,6 @@ gen12_csb_parse(const struct intel_engine_execlists *execlists, const u32 *csb)
 	 * use polling mode.
 	 */
 	GEM_BUG_ON(GEN12_CTX_SWITCH_DETAIL(upper_dw));
-
 	return false;
 }